Electrode element for dry disk rectifiers



May 99 i944., s. RUBEN ELECTRODE ELEMENT FOR DRY DISK RECTIFIERS Filed March 25, 1941 Patented May 9, 1944 UNITED STATES PATENT OFFICE ELECTRODE ELEMENT FOR DRY DISK RECTIFIERS This invention relates to electrode elements for dry disk rectifiers and methods of making the same.

An object on the invention is to improve such electrode elements.

Another object is to improve the method 4vof making said elements.

Other objects of the invention will be apparent from the following description and accompanying drawing taken in connection with the appended claims.

The invention comprises the features of construction, combination of elements, arrangement of parts, and methods of manufacture and operation referred to above or which will be brought out and exemplifiedl in the disclosure hereinafter set forth, including the illustrations in the draw- In the drawing: Figure 1 illustrates a step in the preferred method of making an electrode element according to the present invention involving pouring of molten cuprous sulfide into a mold;

Figure 2 illustrates a subsequent step in the process comprising hot rolling of the cast ingot:

Figure 3 illustrates a fu'ither step involving punching of the rolled sheet into disks or washers;

Figure 4 illustrates a further sulfiding step;

Figure 5 shows surface grinding of the disks;

Figures 6 and 7 illustrate a completed electrode element, while Figure 7a shows an'electrode element of the prior art; and I Figure 8 shows a completed rectifier assembly.

This invention relates to the elements for recvtifiers of the type described in my patents,

#1,751,359 and #2,032,439 and other of my patents dealing with dry disk electric current rectiers. The invention relates particularly to the improvement of the electro-negative electrode elements, which usually are in the form of disks or washers of copper compounds such as cupric sulfide.

Heretofore cupric sulfide disks for dry disk rectifiers have usually been produced by heating a copper Washer in a sulfur vatmosphere until the copper' has been converted into cupric sulde. However, when disks of pure copper are used the resulting cupric sulfide disks are quite easily crushed or broken due to the internal crystal structure produced during conversion of the copper to cupric sulfide. Considerable improvement has been achieved by the use of copper alloys such as an alloy of 85% copper and 15% zinc.

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During sulflding the zinc appears to migrate to the middle of the disk forming a layer of zinc sulfide within the disk which increases the crushing strength of the sulflded disks. However, the layer of zinc sulfide, being of low electrical conductivity, is not as desirable as would be a core of high strength and good electrical conductivity. Likewise, the strength of the suliided disks is not as great as could be desired due to insufficient bonding between the cupric sulfide outer layer and the zinc sulfide core, and hence a considerable loss has been experienced due to breakage of disks during surface grinding.

My Patent #2,198,843 describes a further improvement involving a mercury treatment of the copper-zinc alloy prior to sulding. This has ref sulted in a denser structure having higher degrees of bonding between the cupric sulfide layer and the zinc sulfide core in the finished disk and has greatly reduced the loss due to cracking ofthe disks during grinding. However, the presence of the high resistance zinc sulfide layer in such disks still prevents maximum possible eiliciency from being obtained in the completed rectier.

The present invention contemplates a disk having. a uniform dense structure of cupric sulfide of high crushing strength and good electrical conductivity vand a method of making the same.

The element produced according to the presentinvention also permits the use of much higher contact pressures between cooperating electrodes in the completed rectifier assembly resulting in rectifiers of longer life and better operating characteristics. Briefly the preferred method comprises first producing cuprous sulfide in disk form and then further sulding the cuprous sulfide disks to produce the final cupric sulfide electrode elements.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the meth.. od of procedure and the construction of parts without departing from the spirit of the invention. In the following description and in the claims, parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

The preferred method of manufacture of cupric sulfide electrode elements is as follows, reference being made to the accompanying drawing which illustrates certain steps of the process:

Cuprous sulde is produced by heating copper powder or scrap with sulfur in a Crucible. For

and having cooperating recesses therein providing a mold cavity I5 which may, for example, be 1/ inch thick, 31A, inches wide and 12 inches long. The mold is preferably heated to 500 C. before the molten cuprous sulfide is poured into it in. the manner illustrated in Figure 1.

The ingot of cuprous sulfide is extracted from the mold and is hot rolled at a temperature between 550 C. and 650 C., as is diagrammatically illustrated in Figure 2 wherein the slab I6 of cuprous sulfide is shown being passed through a heating furnace I 'l before passing between rolls I8 and I9 which reduces its thickness. The reduction per pass may preferably amount to to 18% for the first passes and thereafter 18 to 25%.

After being rolled down to the desired thickness such as 60 mils, the rolled strip is heated to about 500 C. and punched into disks or washers by means of a compound die. As illustratedin Figure 3 the sheet IS is passed through a pre-heating furnace 20 to be raised to the desired punching temperature and is then punched by compound die parts 2I, 22, 23 to produce a. circular washer. The die parts preferably also flatten the disks. after the punching operation.

The punched disks coming from the die may, if desired, at this point receive a preliminary rough surface grinding operation of the typev illustrated in Figure 5.

The disks are then placed on a suitable rack and heated in a sulfur atmosphere to convert the cuprous sulfide to cupric sulfide. This may be accomplished, for example, as illustrated in Figure 4 wherein the disks 24 are suspended on suitable racks in sealed sulding chamber containing sulfur 40 and heated by gas heater 26 to produce sulfur vapor. Satisfactory sulfiding may be obtained by heating in this manner in the sulfur vapor for about 4 hours at a temperature about 460 C. and then slowly cooling the elements without contact with the air until they reach room temperature. The sulfur vapor converts cuprous sulfide to cupric sulfide during the sulfiding operation.

Where the equipment is available the sulfur vapor atmosphere may be provided at elevated pressures and the temperature can be raised. This increases the speed of sulfiding and penetration of the sulfur reducing the time of reaction to insure entire sulding. It is also possible to immerse the cuprous sulfide disks in liquid sulfur at a temperature of about 225 C. and then raise it to 450 C. where it is held for several hours after which the temperature is reduced and the disks, now converted to cupric o sulfide, raised above the surface of the liquid sulfur and allowed to drain before cooling down to room temperature.

The sulfided disks, which have now been converted to cupric sulfide are finally ground fiat and smooth by a surface grinding operation such as that illustrated in Figure 5 wherein the disks 24 are carried by movablebelt 21 under a rotating grinding wheel 28, the grinding operation being applied first to one then the other surface of the disks. This grinding operation removes any surface irregularities and produces a smooth fiat surface which is desirable for obtaining the most contact area with the cooperating electrode of magnesium or other material, and prevents localized pressure points in the rectifier assembly. Figure 6 is a perspective view of a completed cupric sulfide disk 24 of the present invention and Figure 7 is a cross section thereof indicating that the structure is dense and uniform throughout, similar to the structure of metal.

Figure 7a shows, for purposes of comparison, a cupric sulfide rectifier element of the prior art 29, specifically an element of the type described.

in my Patent #2,198,843. This prior art element, it will be noted, comprises a core 30 composed principally of zinc sulde, an intermediate thin layer 3| of cupric sulfide crystals of one form and an outer layer 32 of cupric sulfide crystals of a needle-like structure.

Figure 8 shows a completed rectifier assembly embodying cupric sulfide electrode element 24 of the present invention. The electrode element 24 is engaged on one side by a disk 33 of electropositive metal such as magnesium and on the other side by a non-polarizing layer 34 such as carbonized nickel or the like. The assembly is clamped between a pair of radiator and terminal plates 35 and 36 by a bolt 31 insulated from plate 36 by suitable insulating washer 38.

While the present invention has been described as appliedl specifically to cupric sulfide electrodes and the product thereof, the process can also be utilized in the production of electro-negative electrodes of compounds of copper with other sulfur group elements such as selenium and tellulium. In one case a cupric selenide disk ls produced and in the other a disk of cupric telluride.

It will be observed that the present invention describes a cupric compound electrode element of high conductivity and density of uniform` structure and high crushing strength.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What isclaimed is:

1. The method of making an electrode disk element for a dry disk rectifier, which comprises producing a disk of cuprous compound of copper with an element selected from -the group consisting of sulfur, selenium, and tellurium and heating said disk in contact with an excess of said element to convert it to a disk of the cupric compound of said element.

2. The method of making a cupric sulfide electrode of dense uniform structure which comprises producing a dense uniform plate of cuprous sulfide and sulfding said plate to convert it to cupric sulfide.

3. 'I'he method of making a cupric sulfide electrode of dense uniform structure which comprises producing a dense uniform plate of cuprous sulfide and sulfiding said plate by heating it in contact with excess sulfur to convert itto cupric sulfide.

4. The method of making a dry rectifier electrode which comprises casting a cuprous compound of copper with an element selected from the group consisting, of sulfur, selenium and tellurium into a block, reducing said block to a layer and heating said layer in contact with an excess of said element to convert it to a layer of the cupriccompound of said element.

5. The method of making adry rectifier electrode which comprises casting a cuprous compound of copper` with an element selected from the group consisting of sulfur, selenium and tellurium into a block, reducing said block into a plate, punching disks from said plate and heating said disks in contact with an excess of said element to convert them to disks of the cupi-ic compound of said element.

6. The method of making a dry rectifier electrode disk which comprises casting a cuprous compound of copper with an element selected from the group consisting of sulfur, selenium and teilurium into a block, rolling said block into a plate, punching disks from said plate and heating said disks in contact with an excess of said element to convert them to disks of the cupric compound of said element and removing any irregularities from the :faces of said disks.

'7. The method of making a cupric sulde rectiiier electrode disk of dense uniform structure which comprises casting cuprous sulde into a block, hot rolling said block into a plate, punching disks from said plata-heating said disks in contact with an excess of heated sulfur to convert them to cupric sulfide disks and removing any irregularities in the surfaces of said disks.

SAMUEL RUBEN. 

